Shooting Fluorescence Underwater

In this article from The Underwater Photography Show, we'll be diving into the fascinating and often magical world of underwater fluorescence photography, a technique that transforms ordinary subjects into glowing works of art.

Fluorescence photography is different from regular photography because it doesn't rely on reflected light. Instead, it captures a phenomenon where certain pigments absorb light at one wavelength and emit it at another. For instance, a pigment might absorb a blue light and emit an orange one. This process is similar to how certain items, like teeth or white clothes, glow under a blacklight at a disco. You've probably seen this effect already in diving, as many modern diving gear items, like bright pink fins, use fluorescent pigments to look vibrant even at depth. It's a key distinction from bioluminescence, which is light actively emitted by an organism through a chemical reaction, like the sparkling plankton, ostracods, or flashlight fish you see on night dives. Unlike bioluminescence, fluorescence requires an external light source to activate. [0:39]

To capture this effect, we use blue light underwater for stills and UV light for video, since continuous UV lights are easier to find than UV strobes. While UV torches can be used for stills, they require a lot of power for good image quality and depth of field, often resulting in long exposures that produce blurry photos. The best method is to modify strobes with filters. [3:54] We use blue excitation filters on our strobes to convert their light output into a deep blue light that triggers the fluorescent pigments. Examples include filters from Glow Dive and Fire Night Dive, which can strap or mount onto strobes. This makes everything in the water appear dark blue, except for the subjects that are fluorescing. To ensure only the glowing colors are captured, we attach a yellow barrier filter to the lens, which blocks the blue light and allows only the emitted fluorescent colors like green, yellow, orange, and red to reach the camera's sensor. [5:46]

This technique often results in very dark images because of the heavy filtering and the dim nature of fluorescence. To get the best results, we recommend using powerful strobes and a camera with good high-ISO performance. Clustered strobes around the port can also help maximize the light on your subject. One of the great benefits of fluorescence photography is that backscatter doesn't fluoresce, so it's a fantastic technique for low-visibility conditions. The backgrounds in these photos often appear black because non-fluorescent areas don't emit light. [8:37]

While most photographers use this technique with macro lenses, it works well for wide-angle photography too. You can use gel filters taped to the back of a fisheye or other wide-angle lens, which is great for compact setups and allows you to cluster strobes close to the port. When it comes to strobes, smaller, cheaper ones with a colder, bluer light can sometimes perform better, as manufacturers often coat the tubes of larger strobes to reduce the blue tones. You can even wear a yellow filter on your mask to spot fluorescing subjects more easily, though it's not a necessity. [11:02]

Fluorescence photography is a great way to liven up night dives, especially on liveaboard trips or in temperate waters. The best results are found in dark conditions to prevent ambient light from overpowering the dim fluorescence. Exciting subjects to look for include corals, anemones, and tunicates, as well as marine life like eels, scorpionfish, and crustaceans. It's a great artistic endeavor, allowing you to create unique pictures by adjusting the white balance in post-processing. After many macro dives, this technique can help you see and shoot familiar subjects in a completely new way.